Folded and glued paperboard “lockbottom” or “autobottom” cartons (also know by other names, including “folded-bottom boxes”) are generally flat as produced, but are characterized by having one edge portion that is much thicker than the opposite edge portion. The thicker edge portion (which normally forms the bottom part of the carton, when erected) consists of multiple plies (typically five) of the construction material, whereas the thinner edge portion (which normally comprises the cover) is typically of only one- or two-ply thickness. When a number of such cartons are stacked together with the same orientation, the resulting batch is of wedge-like form.
To accommodate that characteristic, lockbottom cartons are conventionally loaded into shipping cases as alternating batches of a multiplicity of cartons, arranged in opposite directions with the thicker end of one batch mated with, or complementary to, the thinner end of the adjacent batch. Doing so serves of course to most efficiently utilize the capacity of the shipping case while, at the same time, affording uniform weight distribution.
The systems for handling and loading such collapsed cartons are usually operatively connected directly to the machines by which they are folded and glued, from which they are presented as a shingled stream in which the thicker end portion of each carton is disposed as the leading edge with respect to the machine travel direction. As a practical matter, therefore, the packaging machines are also designed to handle cartons so oriented.
By way of further description, packaging of batches of lockbottom cartons, in an alternating arrangement, is depicted in FIG. 1 of the drawings; each carton is designated “C,” the alternating batches of cartons (in this instance, consisting of five cartons) are designated “B” and “B′,” and the corrugated shipping case (shown in broken line) contains a count of 60 cartons and is designated S. An individual carton C is also shown in FIG. 2, and a stacked batch B of ten cartons is shown in FIG. 3.
Machines for automatically transferring continuously arriving “folded-bottom boxes,” to enable packaging as alternating batches in shipping cases, have previously been provided. One such machine is described in Bensberg et al. U.S. Pat. No. 5,078,260, and is depicted in FIGS. 8-10 of the appended drawings. Although, in most respects, the article-transfer system disclosed by Bensberg et al. is effective for its intended purposes, it nevertheless suffers from a fundamental deficiency, which in fact is believed to have rendered the system functionally and commercially unsuccessful.
That deficiency is indeed discussed in the passage beginning at line 16 in column 4 of the patent: “Since the alternating lay-off from the two conveyor mechanisms 3 and 4 makes its impossible to guide folded-bottom boxes 16, which have a tendency to hook onto one another, over the total lay-off area 11, the boxes are maintained at an angle to the direction of travel as they leave conveyor mechanisms 3 and 4 by rods 14.1 and 14.2 or 15.” Although the rods provided do assist in reducing the “tendency to hook onto one another,” they do not adequately solve the problem.
The reason why hooking (or catching, or interlocking) of cartons occurs during such automatic “overstocking” is illustrated in FIG. 4 of the appended drawings. When the cartons C (moving in the direction of the large, open arrow) arrive at the accumulation area, where they merge and accumulate as a shingled (or imbricated) stream, half are oriented with their relatively smooth, planar surfaces (hereinafter referred to for convenience as the “continuous” side) oriented upwardly (as seen for example in FIGS. 1-3), whereas the other half arrive in the inverted orientation shown in FIG. 4. When the continuous sides, generally designated by the numeral 15, face upwardly, successive cartons readily slide over one another, for trouble-free overstacking. In the inverted orientation, however, the upwardly facing side of the carton, generally designated by the numeral 25, is discontinuous, being comprised of panels that lie in at least two parallel planes and that present a free, generally transverse intermediate edge E at the intersection of the planes. When a deposited carton has its discontinuous side 25 facing upwardly, the leading edge of a successive carton will have a tendency to catch on, or interlock with, the exposed intermediate edge structure E of the underlying carton, as indicated by the three triangular marks in FIG. 4, usually necessitating stoppage of the entire production line when that occurs.